Closed-Loop Insulin System Improves Glucose Control in Pregnant Women with Type 1 Diabetes: JAMA
Canada: The randomized CIRCUIT trial has found that pregnant women with type 1 diabetes who used a closed-loop insulin delivery system spent significantly more time within the pregnancy-specific glucose range, with less time above or below targets, and lower average glucose and HbA1c levels compared to those receiving standard care.
The multicenter study, led by Dr. Lois E. Donovan from the Department of Medicine, Cumming School of Medicine, University of Calgary, Canada, and published in JAMA, provides compelling evidence supporting the use of closed-loop insulin delivery—commonly known as an artificial pancreas—during pregnancy in women with type 1 diabetes.
Pregnancy in women with type 1 diabetes poses unique challenges in maintaining tight glucose control, as even minor fluctuations in blood glucose can increase the risk of complications for both mother and baby. Around half of such pregnancies are associated with hyperglycemia-related complications, highlighting the urgent need for improved glucose management approaches.
The CIRCUIT trial was an open-label, randomized clinical study conducted across 14 centers in Canada and Australia. It enrolled women with type 1 diabetes before 14 weeks of gestation, with participants followed up until six weeks after delivery. Recruitment took place between June 2021 and July 2024, and follow-up was completed in March 2025.
A total of 94 pregnant women were enrolled, of whom 91 were randomized to either closed-loop insulin therapy (n = 46) or standard care (n = 45), which included insulin pump therapy or multiple daily injections, along with continuous glucose monitoring. The primary measure of efficacy was the proportion of time that participants’ glucose levels remained within the pregnancy-specific target range of 63 to 140 mg/dL, monitored between 16 and 34 weeks of gestation.
The key findings of the study were as follows:
- Women using the closed-loop insulin delivery system spent an average of 65.4% of the time within the pregnancy-specific glucose range, compared to 50.3% in the standard care group.
- This difference was statistically significant, with an adjusted mean difference of 12.5 percentage points.
- Participants in the closed-loop group showed lower mean glucose levels and reduced HbA1c values, reflecting improved overall glycemic control.
- One episode of severe hypoglycemia occurred in the closed-loop group.
- Two cases of diabetic ketoacidosis (DKA) were reported in the closed-loop group, while one case was observed in the standard care group.
Despite these occurrences, the overall findings strongly favored the use of closed-loop insulin delivery for achieving optimal glycemic management during pregnancy.
According to the authors, the findings demonstrate that automated insulin delivery systems can substantially enhance glucose regulation during pregnancy—a period when tight control is often difficult to achieve. The technology dynamically adjusts insulin dosing based on real-time glucose readings, reducing the burden of manual insulin management.
"The CIRCUIT trial establishes that closed-loop insulin systems can help pregnant women with type 1 diabetes maintain blood sugar levels closer to the recommended range, potentially lowering the risk of maternal and neonatal complications. These results reinforce the growing role of technology-driven diabetes care in improving outcomes for high-risk pregnancies," the authors concluded.
Reference:
Donovan LE, Lemieux P, Dunlop AD, et al. Closed-Loop Insulin Delivery in Type 1 Diabetes in Pregnancy: The CIRCUIT Randomized Clinical Trial. JAMA. Published online October 24, 2025. doi:10.1001/jama.2025.19578
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